1. Field of the Invention
The present invention relates to heat exchangers and a method for manufacturing the same, and more particularly to an improved connection structure and connection method between a tank and a fluid pipe for heat exchangers.
2. Description of the Related Art
In a conventional heat exchanger having a tank and a fluid pipe connected to the tank, for example, a fluid inlet pipe or outlet pipe, brazing between the tank and the fluid pipe may be performed as follows. For example, FIG. 9 depicts a heat exchanger tank 104 having a pipe insertion hole 102 disposed in tank wall 103 of tank 104. A burr 101 may be formed around pipe insertion hole 102 to increase the surface area of tank 104 contacting fluid pipe 105, i.e., to enlarge the brazing area between tank 104 and fluid pipe 105. An end portion of fluid pipe 105 may be inserted into pipe insertion hole 102 so that a tip 110 of fluid pipe 105 may be positioned over a tip 111 of burr 101. The inserted fluid pipe 105 may be temporarily fixed to tank 104 by spot welding 106. Annular brazing material 107 may be placed around the periphery of fluid pipe 105 and brought into contact with an outer surface 108 of tank wall 103. Then, the assembly may be is heated in a furnace, whereby fluid pipe 105 is brazed to tank 104.
In such a conventional connecting and brazing structure, when the assembly is heated in a furnace, if any vibration occurs, annular brazing material 107 may shift away from outer surface 108 of tank wall 103. If shifting occurs, an insufficient amount of molten brazing material may remain in contact with burr 101 and fluid pipe 105 to form a good brazed and connected state between fluid pipe 105 and tank 104.
Further, the portion of fluid pipe 105 inserted into the interior of tank 104 is often relatively long. Consequently, the portion disrupts fluid flow in tank 104 resulting in significant pressure loss of fluid flow in the tank 104.
Furthermore, the contact area, i.e., brazing area, between tank 104 and fluid pipe 105 is relatively small. Hence, the connection strength between fluid pipe 105 and tank 104 may be insufficient.